1. Field of the Invention
This invention relates to a process for hydroconverting coal in a hydrogen donor solvent to liquid hydrocarbon products in the presence of a catalyst prepared in situ from a small amount of metals added to the mixture of coal and solvent as oil soluble metal compounds.
2. Description of the Prior Art
Hydroconversion of coal to coal liquids in a hydrogen donor solvent process is well known. In such a process, a slurry of coal in a hydrogen donor solvent is reacted in the presence of molecular hydrogen at elevated temperature and pressure. See, for example, U.S. Pat. No. 3,645,885, the teachings of which are hereby incorporated by reference. The hydrogen donor solvent which becomes hydrogen depleted during the coal liquefaction reaction, in the prior art processes, is generally subjected to a hydrogenation stage prior to its being recycled to the hydroconversion zone.
It is also known to convert coal to liquid products by hydrogenation of coal which has been impregnated with an oil-soluble metal naphthenate or by hydrogenation of coal in a liquid medium such as an oil having a boiling range of 250.degree. to 325.degree. C. containing an oil-soluble metal naphthenate, as shown in Bureau of Mines Bulletin No. 622, published 1965, entitled "Hydrogenation of Coal in Batch Autoclave", pages 24 to 28. Concentrations as low as 0.01% metal naphthenate catalysts, calculated as the metal, were found to be effective for the conversion of coal. U.S. Pat. Nos. 3,532,617 and 3,502,564 also disclose the use of metal naphthenates in coal hydroconversion.
U.S. Pat. No. 3,920,536 discloses a process for the liquefaction of subbituminous coal in a hydrogen donor oil in the presence of hydrogen, carbon monoxide, water, and an alkali metal or ammonium molybdate in an amount ranging from 0.5 to 10 percent by weight of the coal.
It has now been found that hydrogen depletion of the hydrogen donor solvent in the coal hydroconversion zone (liquefaction zone) can be minimized and the necessity for rehydrogenating the used hydrogen donor solvent can be reduced or omitted when the hydroconversion reaction is conducted in the presence of a minor amount of a catalyst produced from an added oil-soluble metal compound.
Additional advantages in the utilization of oil-soluble metal compounds in a hydrogen donor solvent coal liquefaction process will become apparent in the following description.
The term "hydroconversion" with reference to coal is used herein to designate a catalytic conversion of coal to liquid hydrocarbons in the presence of hydrogen.